How is that possible though. Android is the same accross the board is it not? Apart from a few cosmetic changes from manufacturers and some additional software that might be installed from them?
There can actually be a fair amount of difference. That being said, I'd be surprised if push functionality is one of them, because thats fairly high level.
The things that can differ between different builds of android are:
Device dependent software - ie drivers for the radio interfaces, touchscreen, keyboard and camera
The kernel - also hardware dependent I think. The kernel, mostly based off the linux kernel, is the heart of the operating system.
The user interface - launcher, homescreens etc
The installed applications - like LG Mail instead of regular Google Mail.
Anyway, as I said, I dont think any of that should affect push functionality, except maybe the radio hardware but I'd be surprised if there was a problem there. try googling to see if other people with the same phone as you have problems with push functionality.